net.i2p.data

Class Destination

java.lang.Object

net.i2p.data.DataStructureImpl

net.i2p.data.KeysAndCert

net.i2p.data.Destination

All Implemented Interfaces:

Serializable, DataStructure

Direct Known Subclasses:

VerifiedDestination

public class Destination
extends KeysAndCert

Defines an endpoint in the I2P network that can receive messages.

Destination represents the fundamental addressing and identity concept in I2P:

• Network Endpoint: Messages sent to a Destination will find it regardless of location
• Cryptographic Identity: Contains encryption and signing keys
• Certificate: Optional metadata about the identity
• Addressing: Can be encoded as Base64 or Base32 (.b32.i2p)
• Immutability: Identity becomes immutable after keys are set

Key Components:

• Public Encryption Key: Historically used for end-to-end encryption
• Signing Public Key: Used for identity verification and LeaseSet signing
• Certificate: Optional metadata (NULL, HIDDEN, SIGNED, etc.)
• Cached Hash: SHA-256 hash for efficient identification

Address Formats:

• Base64: Full binary encoding for configuration files
• Base32: Human-readable .b32.i2p addresses
• Hash: 32-byte SHA-256 for internal identification

Historical Changes:

• Pre-0.6: Public key used for end-to-end encryption
• Post-0.6: End-to-end encryption removed, LeaseSet keys used instead
• LeaseSet Encryption: Public key first bytes used as IV (deprecated)
• 0.9.9: Immutable after keys and certificate are set

Usage:

• Client Connections: Target for I2P client communications
• Service Hosting: Identity for hosting I2P services
• Message Routing: Destination for I2NP message delivery
• Address Book: Entry in address books and contact lists

Security Considerations:

• Key Protection: Private keys must be securely stored
• Identity Verification: Always verify signatures from destinations
• Certificate Validation: Check certificate types and content
• Deprecated Features: Avoid legacy encryption mechanisms

Performance Features:

• Caching: LRU cache for frequently used destinations
• Lazy Computation: Base32 address computed on demand
• Efficient Storage: Optimized memory usage and serialization
• Fast Lookup: Hash-based identification for quick comparisons

Immutability:

• After 0.9.9: Keys and certificate cannot be changed after setting
• Thread Safety: Immutable objects are inherently thread-safe
• Corruption Prevention: Protects against accidental modification
• Exception: Modification attempts throw IllegalStateException

Migration Notes:

• Legacy Encryption: Public key usage deprecated in favor of LeaseSet encryption
• Modern Alternatives: Use EncryptedLeaseSet for proper encryption
• IV Generation: LeaseSet encryption IV should not use public key bytes

See Also:

Serialized Form

Field Summary

Fields inherited from class net.i2p.data.KeysAndCert

_certificate, _paddingBlocks, _publicKey, _signingKey

Constructor Summary

Constructors

Constructor and Description
Destination()
Destination(String s) alternative constructor which takes a base64 string representation

Method Summary

Modifier and Type	Method and Description
static void	clearCache() Clear the cache.
static Destination	create(InputStream in) Pull from cache or return new
boolean	equals(Object o)
int	hashCode() the signing key has enough randomness in it to use it by itself for speed
int	size()
String	toBase32() For convenience.
String	toBase64() Cache it.
int	writeBytes(byte[] target, int offset) Deprecated, used only by Packet.java in streaming.

Methods inherited from class net.i2p.data.KeysAndCert

calculateHash, combinePadding, getCertificate, getEncType, getHash, getPadding, getPublicKey, getSigningPublicKey, getSigType, isCompressible, readBytes, setCertificate, setPadding, setPublicKey, setSigningPublicKey, toString, writeBytes, writePaddingBytes

Methods inherited from class net.i2p.data.DataStructureImpl

fromBase64, fromByteArray, read, toByteArray

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Constructor Detail

Destination

public Destination()

Destination

public Destination(String s)
            throws DataFormatException

alternative constructor which takes a base64 string representation

Parameters:

s - a Base64 representation of the destination, as (eg) is used in hosts.txt

Throws:

DataFormatException

Method Detail

clearCache

public static void clearCache()

Clear the cache.

create

public static Destination create(InputStream in)
                          throws DataFormatException,
                                 IOException

Pull from cache or return new

Throws:

DataFormatException

IOException

equals

public boolean equals(Object o)

Overrides:

equals in class KeysAndCert

hashCode

public int hashCode()

Description copied from class: KeysAndCert

the signing key has enough randomness in it to use it by itself for speed

Overrides:

hashCode in class KeysAndCert

size

public int size()

toBase32

public String toBase32()

For convenience.

Returns:

"{52 chars}.b32.i2p" or null if fields not set.

toBase64

public String toBase64()

Cache it. Useful in I2PTunnelHTTPServer where it is added to the headers

Specified by:

toBase64 in interface DataStructure

Overrides:

toBase64 in class DataStructureImpl

Returns:

null on error

writeBytes

public int writeBytes(byte[] target,
                      int offset)

Deprecated, used only by Packet.java in streaming. Broken for sig types P521 and RSA before 0.9.15

Returns:

the written length (NOT the new offset)